1. Field of the Invention
This invention relates generally to polyimides. It relates particularly to modifications of the polyimide formed by reaction of 3,3',4,4'-benzophenonetetracarboxylic dianhydride and 1,3-bis(4-aminophenoxy-4'-benzoyl)benzene, whereby the resulting compositions are easily compression molded.
2. Description of the Related Art
The semicrystalline polyimide formed by reaction of 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA) and 1,3-bis(4-aminophenoxy-4'-benzoyl)benzene (1,3-BABB) has been demonstrated to possess excellent film properties in its high molecular weight form (P. M. Hergenrother and S. J. Havens, U.S. Pat. No. 4,820,791; and P. M. Hergenrother, N. T. Wakelyn, and S. J. Havens, J. Polym. Sci.; Part A: Polym. Chem., 25, 1093 (1987)). These properties include high tensile strength and modulus and excellent resistance to chemicals. However, efforts to fabricate this high molecular weight polyimide into composite or adhesive panels require the use of high temperatures and high pressure, which conditions are needed for polymer consolidation. For example, a bonding temperature of 400.degree. C. at a pressure of 1000 psi was required to bond titanium to titanium tensile shear specimens. This bonding pressure is in excess of that which can be applied in many commercial processes.